LAS VEGAS — Bernard Hopkins suddenly ended a close fight with two left hooks to the body in the ninth round Saturday night to stop Oscar De La Hoya and ruin his bid to become the undisputed middleweight champion.

The punches put De La Hoya on the canvas on his hands and knees in obvious pain. When De La Hoya rolled over on his back, referee Kenny Bayless stopped the fight at 1:38 of the ninth.

While Hopkins celebrated, De La Hoya remained on his knees, his face buried in his gloves. He repeatedly pounded the canvas in frustration after being stopped for the first time in his brilliant career.

“I felt a sense of urgency,” Hopkins said. “I wasn’t sure if I was winning or not.”

Hopkins (45-2-1, 32 knockouts) was ahead on two scorecards and behind on a third in a cautiously fought bout when he suddenly landed the punches just below De La Hoya’s rib cage to retain his undisputed middleweight title in his 19th title defense.

“A well-placed body shot,” De La Hoya said.

De La Hoya (37-4, 29 knockouts) was a 2-1 underdog in only his second fight as a middleweight and was taking on a champion who hadn’t lost in 11 years.

“I tried to do the impossible on paper — beat the middleweight champ coming up from 130 pounds,” De La Hoya said.

Hopkins fought cautiously the first half of the fight, giving De La Hoya and the sold-out crowd at the MGM Grand arena some cause for optimism. De La Hoya, who many thought would box and move, was the aggressor in many of the early exchanges as he moved forward against Hopkins.

“He came to fight,” Hopkins said. “He didn’t come to run or look for a gift from the judges.”

The pro-De La Hoya crowd cheered their fighter from the opening bell, screaming every time he landed a punch. Hopkins fought patiently, but as the rounds went on, his corner told him to pick up the pace and pressure De La Hoya more.

Still, De La Hoya was holding his own until the fight came to a stunning climax that quieted the shocked crowd as De La Hoya stayed on the canvas.

“He caught me right on the button,” De La Hoya said. “Believe me, I tried getting up but I couldn’t. I have what it takes, but he hit me right on the button.”

De La Hoya, who weighed 155 pounds to 156 for Hopkins, had fought only once as a middleweight, but his opponent this time was a big upgrade from little known Felix Sturm.

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